Conventionally, technology for enhancing the performance of studless tires on ice (braking performance and driving performance) are known (for example, see International Patent Publication No. WO/2010/032606). The pneumatic tire disclosed in International Patent Publication No. WO/2010/032606 includes a tread pattern with a plurality of blocks tightly arranged in a honeycomb-shape.
Generally, when a form of the blocks partitioned by grooves is anisotropic, resistance to external forces tends to increase only in a specified direction, thus enhancing a specific aspect of tire performance. For example, when the resistance to external forces in the tire circumferential direction is boosted making the form of the blocks anisotropic in the tire circumferential direction, braking performance on snow and braking performance on ice are enhanced.
Further, when the form of the grooves that partition the blocks is made anisotropic, drainage performance tends to be enhanced. For example, when the tire width direction grooves with a V-profile are provided, the side of the blocks, partitioned by these grooves, that makes first contact with the ground (leading edge) is the apex of the V shape. Thus, water is efficiently drained from the grooves and drainage performance can be enhanced.
In the pneumatic tire disclosed in International Patent Publication No. WO/2010/032606, the form of the blocks is not anisotropic in any direction. Therefore, it is unclear whether the above-described pneumatic tire provides braking performance on ice, braking performance on snow, and drainage performance in a well-balanced manner.